Roundball, I certainly agree that the preasures involved in the breech of any muzzleloader is many times that found in an engine. I feel that propperly installed, Heli-coil will sustain these preasures. "But" it also presents a catch basin for corrosive deposits to work on the metal. As was said if the part has to be removed many times over the years,this certainly could create a problem. I,m interested in obtaining a bbl. and install a breech plug of my own design.As I stated, if anyone has received a bbl. in .62cal.and would like to recoup their investment. I prefer a smoothie,but would settle for rifled. [email protected]